Doctors treat young victims injured by automatic weapons and rocket propelled grenades at Baghdad's Yarmouk Hospital Monday, July 17, 2006, in Iraq. Dozens of heavily armed attackers raided an open air market Monday in a tense town south of Baghdad, killing at least 41 people and wounding 42, police and hospital officials said. Most of the victims were believed to be Shiites. (AP Photo/Samir Mizban) less

Doctors treat young victims injured by automatic weapons and rocket propelled grenades at Baghdad's Yarmouk Hospital Monday, July 17, 2006, in Iraq. Dozens of heavily armed attackers raided an open air market ... more

Photo: SAMIR MIZBAN

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A woman cries as doctors treat her husband, a victim of gunfire at a open market, Monday, July 17, 2006, at Baghdad's Yarmouk Hospital in Iraq. Dozens of heavily armed attackers raided an open air market Monday in a tense town south of Baghdad, killing at least 41 people and wounding 42, police and hospital officials said. Most of the victims were believed to be Shiites. (AP Photo/Samir Mizban) less

A woman cries as doctors treat her husband, a victim of gunfire at a open market, Monday, July 17, 2006, at Baghdad's Yarmouk Hospital in Iraq. Dozens of heavily armed attackers raided an open air market Monday ... more

2006-07-18 04:00:00 PDT Baghdad -- Dozens of gunmen suspected of being Sunnis went on a rampage through a mostly Shiite market district in the town of Mahmoudiya on Monday, killing at least 48 people and wounding scores of others, police officials said.

Many of the attackers, who fired assault rifles, heavy machine guns and rocket-propelled grenades, wore the uniforms of the Iraqi security forces.

"You can't tell your friend from your enemy," an Iraqi army officer said as Iraqi troops moved in.

The daylight killings in Mahmoudiya, 20 miles south of Baghdad, increased fears among Iraqis that the country may be sliding into full-scale civil war and prompted a crucial Shiite bloc to storm out of Parliament, protesting the lack of security.

The Mahmoudiya attack and other violence Monday brought to nearly 100 the number of people killed in two days in Iraq, making it one of the deadliest periods since the appointment of a new government in May.

The latest deaths underscored the government's inability to tamp down spiraling cycles of sectarian violence that, more and more, are characterized by execution-style reprisal killings.

An obscure guerrilla group, the Supporters of the Sunni People, posted an Internet message saying it had carried out the Mahmoudiya attack to avenge a massacre of Sunni Arab civilians by Shiite militiamen in Baghdad on July 9.

The killings have widened the political fault lines in the Shiite-led government of Prime Minister Nouri al-Maliki. The legislators who walked out of Parliament on Monday were followers of the radical Shiite cleric Muqtada al-Sadr, whose militia has been engaged in increasingly frequent battles with American-led forces. Many Iraqi officials believe that al-Sadr's participation in the political process is indispensable to achieving stability in Iraq, citing his wide following.

Iraqi forces and American soldiers appeared helpless to stop the bloodshed in Mahmoudiya, arriving on the scene after the gunmen had killed dozens of people, witnesses said. The town, a center of Sunni-Shiite conflict, falls under the watch of the 1st Battalion of the 502nd Regiment, 101st Airborne Division, the same unit in which six soldiers have been implicated in the rape of an Iraqi girl in March and the killing of her, a younger sister and their parents.

"It's become obvious that the occupation forces are responsible for the devastation taking place in our country," a senior al-Sadr legislator, Bahaa al-Aaraji, said at a news conference in Baghdad.

He said that the al-Sadr bloc, which holds at least 30 of the 275 legislative seats, was not permanently boycotting the parliament, but had walked out of Monday's session out of fury at both the massacre and recent American and British attacks on al-Sadr followers.

Al-Sadr, who led two rebellions against the Americans in 2004, released a statement last Friday saying Iraqis would not "sit by with folded hands" while Israel battles Hezbollah, the militant Shiite group, along the Lebanese border.

That suggested the possibility of more attacks by his militiamen against the Americans, often criticized by al-Sadr as supporting Israel, and thus widening the firestorm in the Middle East.

The assault in the Mahmoudiya market took place about 9 a.m., as the streets were packed with shoppers and men going to cafes and teahouses.

Explosions from mortars or grenades came first, witnesses and the mayor said, although reports of a car bomb had been issued earlier by some security officials. Then dozens of gunmen rolled up in cars and began walking through the market, shooting people left and right. At least eight cars burst into flames. Bodies lay strewn across the street and slumped in shops and restaurants.

The attack Monday resembled one in the al-Jihad neighborhood of Baghdad on July 9, when Shiite militiamen killed up to 50 Sunnis by dragging people from cars and homes and shooting many in the head. Until recently, such mass killings had been relatively rare in the Iraq war.

The American military has been unable to tame the Mahmoudiya area, which lies on a strategic southern approach to Baghdad and is known as the "triangle of death" because of its prolific body count.